A steel material has been widely applied for the fabrication of rotation axes of air spindle, air roller and ball bearing roller which are employed in precision grinding instruments. However, the steel is, though it is of a high strength, so heavy that balancing cannot be easily accomplished during rotation due to its extremely high inertia. So, aluminum which is much lighter than the steel, has been substituted for the steel. The aluminum, however, has not been practically applied in the art, since its strength is too weak to use in the same area.
To solve the said problems, composite materials such as carbon fiber epoxy composite material and glass fiber epoxy composite material have been developed as substitutes for the metal materials. Since the composite material has a higher specific strength than steel or aluminum, it is lighter than the metal materials with the same strength. Moreover, it has an advantage of minimizing sliding on contact with other mechanical elements because it enables fast start and stop due to its low rotation inertia. Furthermore, its characteristic of controlling vibration is superior to that of steel or aluminum, since it has much higher value of damping factor(about 1%), comparing with that of steel(0.001--0.1%).
However, in the event of fabricating mechanical elements using only the composite material, much material is needed to satisfy both torque-transfer capability and natural frequency. Therefore, instead of using the composite material, it is preferably suggested to employ both a composite material and a metal material such as steel or high strength aluminum which is light and has a superior torque-transfer capability. In this regard, several methods for fabricating mechanical elements have been proposed in the art: a mechanical joining method using bolt or rivet; a joining method using an adhesive cement; and, a concurrent hardening method using a resin remaining in the course of hardening of a composite material on a metal material. However, the mechanical joining method, since it may cause a damage to the composite material, has been hardly employed to the fabrication of main elemes such as axes of spindle or roller. Naturally, the joining method or the concurrent hardening method has been widely used in the art.
In addition, some methods for fabricating mechanical elements using the said composite material have been disclosed so far(see: J. H. Choi and D. G. Lee, J. Adhesion, 44:197 212(1994); W. T. Kim and D. G. Lee, Composite Structures, 30:229-240(1995); S. J. Lee and D. G. Lee, J. Adhesion, 50:165-180 (1995)).
However, air spindle, air roller and ball bearing roller are still fabricated by employing rotation axes made of steel or aluminum materials, in accordance with the conventional methods which have shortcomings discussed as above. Accordingly, there are strong reasons for exploring and developing an improved method for fabricating air spindle, air roller and ball bearing roller.